To create a header graphic optimized for Internet, you
need to use the "Save JPG" feature.

When you click on the "Save JPG" button from the main
Toolbar, XHeader will open a new window asking you to choose the quality of the JPG image.

In this window you will be presented with ten (10)
different versions, each of a different quality and file size. Just pick the one that you feel is the best match
between high quality and small file size.

You can achieve the same result by selecting the "Save
JPG" option from the File menu.